Uncovering Somatosensory Components of the CNS by https://padlet.com/miller8522/h80igdubl26atdrl MM2 1800-1900AD en-us 2021-03-24 01:54:23 UTC 2024-04-09 20:30:45 UTC hello@padlet.com https://padlet.net/icons/png/1f449.png The Discovery of Another Mechanoreceptor! miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345919237 In 1875, German anatomist Friedrich Sigmund Merkel first described one of the other mechanoreceptor cells, now known as Merkel cells, as "touch cells."1 He indicated that these cells were responsible for taking mechanical stimuli and transforming it into neural information2. It was hard to find a lot about Friedrich Sigmund Merkel and his discovery of the Merkel cells, so I chose to include an image of him instead. These cells responsible for slowly adapting neural impulses and are implicated in some diseases including Merkel cell carcinoma.

(1) Halata, Z., Grim, M. and Bauman, K.I. (2003), Friedrich Sigmund Merkel and his “Merkel cell”, morphology, development, and physiology: Review and new results. Anat. Rec., 271A: 225-239. https://doi.org/10.1002/ar.a.10029
(2) Camisa, Charles M.D.; Weissmann, Arthur M.D. Friedrich Sigmund Merkel, The American Journal of Dermatopathology: December 1982 - Volume 4 - Issue 6 - p 527-536]]> 2021-03-24 02:00:30 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345919237 The Homunculus miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345920684 In 1937, Wilder Penfield performed electrical stimulation on over 100 epileptic patients to map the somatosensory cortex- the area of the brain responsible for feeling sensations. He collected this data then had an artist characterize these findings to a cartoon body known as the homunculus, or "little man." The homunculus depicts the sizes of body features with the amount of area they take up in the somatosensory cortex. For example, it shows the hands as some of the largest features because that is where we have a lot of receptors that end up projecting to the corresponding area of the somatosensory cortex1. This was an extremely important finding in the field of neuroscience and is always an important discussion in learning about the somatosensory cortex. The pictures indicate the mapping experiment along with the homunculus on the far right. 

(1) http://www.scholarpedia.org/article/S1_somatotopic_maps

]]> 2021-03-24 02:01:05 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345920684 Pacini's Pacinian Corpuscles miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345921033 The first mechanoreceptors discovered involving the sensation of touch was first observed in 1831 by Filippo Pacini. While in an Italian medical school observing the median and ulnar nerves, he saw tiny oval-shaped bodies attached. He became infatuated about them after he asked his professors what they were and they said they were just fat. He came from a very poor background, and decided to save up his money for a microscope, formally viewing them. He made a sketch of these findings (shown below) in 1840 and declared them related to neurons. The scientific community throughout the 30's were very unamused by his findings. In fact, a previous scientist first described the corpuscles all the way back in the 1740s, but it wasn't formally published until 18481. These mechanoreceptors are found deep within the skin and are responsible for feeling vibrations or pressure.
(1) https://www.ph.ucla.edu/epi/snow/brainresearchbul38(2)_161_165_1995.pdf]]> 2021-03-24 02:01:14 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345921033 Clinical Tricks for Testing Somatosensory System miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345922253 In 1896, Max von Frey developed a clinical test for discovering different pain points on the skin. He used hairs (human or animal-sometimes horse) of different diameters to press onto the skin. Using the technique of pressing the different diameter hairs perpendicular to the surface until they bent, the force applied could be calculated, then it he could map what force was needed to feel the sensation in different areas. Shown below is the map he used to when probing for temperature, pain and touch sensitive spots using probes and electrical devices1. His work carried into modern day clinical techniques, but instead of using hairs, they use nylon microfilaments2.


(1) Pearce, J M S. “Von Frey's pain spots.” Journal of neurology, neurosurgery, and psychiatry vol. 77,12 (2006): 1317. doi:10.1136/jnnp.2006.098970
(2) https://nbtltd.com/wp-content/uploads/2018/10/37450-275-von-frey-hairs-leaflet.pdf]]> 2021-03-24 02:01:42 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345922253 Proprioceptive Somatosensation miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345923381 In 1893, Charles Scott Sherrington introduced the word "proprioceptive" into the field of neurophysiology. He described, “In muscular receptivity we see the body itself acting as a stimulus to its own receptors—the proprioceptors.”1

Sherrington was profound in research on neurons, specifically in synaptic transmission. He founded the term synapse and researched them extensively to understand reflexes and somatosensory perception in his article published in 1907 called "The intergrative action of the nervous system." 2

He won the noble peace prize for physiology or medicine his studies of neurons in 1932. Below is a photo of him from the US National Library of Medicine3.

(1) Charles S. Sherrington, "On the Proprio-ceptive System, Especially in its Reflex Aspect." Brain, Volume 29, Issue 4, March 1907, Pages 467–482, https://doi.org/10.1093/brain/29.4.467
(2) Pearce JMS. Sir Charles Scott Sherrington (1857–1952) and the synapse. Journal of Neurology, Neurosurgery & Psychiatry 2004;75:544.

(3) Sir Charles Sherrington – Photo gallery. NobelPrize.org. Nobel Media AB 2021. Sun. 4 Apr 2021. https://www.nobelprize.org/prizes/medicine/1932/sherrington/photo-gallery/
]]> 2021-03-24 02:02:05 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1345923381 Contemporary Study- The Effect of Aging on Somatosensory System miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1384552074 Unfortunately, the elderly community has a common history of being at risk for injuries associated with falling. A lot of modern research tries to combat this by looking into their declining somatosensory system as well as their balance impairment. In their article, Shaffer and Harrison discuss their findings on impairments in somatosensory function. Clinically they found that anatomically there are less mechanoreceptors within elderly,  their threshold to detect touch increases- meaning they need larger forces to feel the sensation-, and they exhibit impaired proprioception as well. Further studying these impairments could implement better risk factors to prevent falls as well as the relationship to their decline in being able to balance1. Below is a chart from the article showing how physical therapy aims to shift these impairments.


(1) Scott W Shaffer, Anne L Harrison, Aging of the Somatosensory System: A Translational Perspective, Physical Therapy, Volume 87, Issue 2, 1 February 2007, Pages 193–207, https://doi.org/10.2522/ptj.20060083]]> 2021-04-05 19:46:19 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1384552074 Docent- Ramón y Cajal miller8522 https://padlet.com/miller8522/h80igdubl26atdrl/wish/1384778607 To guide my visitors through this museum, I would choose Santiago Ramón y Cajal. He was a Spanish neuroscientist whom many describe as one of the fathers of neuroscience in the early 1900s with his work with The Neuron Doctrine. He is most famous for this, however, he also worked a lot of somatosensory features of the nervous system describing the mechanoreceptors (all of them including the Pacinian and Meissner's corpuscles, Ruffini's endings, and Merkel's disks) as well as nociceptors1. Below is one of his drawings of the nerve endings within a human finger.

(1) William D. Willis, The somatosensory system, with emphasis on structures important for pain, Brain Research Reviews, Volume 55, Issue 2, 2007, Pages 297-313, ISSN 0165-0173, https://doi.org/10.1016/j.brainresrev.2007.05.010.]]> 2021-04-05 21:14:40 UTC https://padlet.com/miller8522/h80igdubl26atdrl/wish/1384778607